HP-UX IP Address and Client Management Administrator's Guide HP-UX 11i v2, HP-UX 11i v3

Figure 1-3 DHCP Client and Server Transaction

The following describes the interaction between the client and the DHCP server in the Figure 1-3

and the steps involved in assigning an IP address to a client on the network:

1. A DHCP transaction begins when a client sends out a DHCP DISCOVER packet which is

usually a broadcast packet. The packet contains only the client’s hardware address.

2. The server receives the DHCP DISCOVER packet. If an IP address on the client subnet is

available and the server is willing to grant a lease, it makes an offer by sending a DHCP

OFFER packet to the client. The offer packet contains the following information:

• Proposed IP address for the client

• Server name

• Server IP address

• Other configuration information

3. The client receives the DHCP OFFER packet. The client may receive more than one offer if

more than one DHCP server exists on the network. HP recommends that you have only one

DHCP server on the network. If the client is interested in the offer, it sends a DHCPREQUEST

packet to the server. This indicates a formal request to lease the IP address offered by the

server.

NOTE: The client rejects offers for IP addresses with short lease times. For example, the

client rejects an offer with a lease time of 10 seconds.

4. The DHCP server receives the DHCPREQUEST packet and leases an IP address to the client.

The server sends a DHCPACK packet to the client. This is an official notification that the

address has been granted.

5. Before the lease time expires, the DHCP client requests to extend the lease by sending a

DHCPREQUEST packet to the server. The server then updates and extends the lease time.

It sends a DHCPACK packet to the client to notify that the lease has been extended. These

updates and lease extensions continue as long as the client is powered on. If the lease expires

and the client is not powered on, and is not able to request an extension on the lease, the IP

address is recycled.

46 Overview